Field of the Invention
This invention relates generally to an apparatus for exercising the hand or fingers and, more particularly, to a hand exerciser which is anatomically, physiologically, and functionally correct. It is well known that after injury to an upper extremity, it is often necessary to immobilize the hand for a period of several days or perhaps several weeks. During this time, as a result, a patient may loose strength in the upper extremity due not only to the injury or surgery, but also due to the atrophy accompanying immobilization of the extremity. When the patient is first allowed to engage in resistive exercise, his grip strength may be less than one pound. However, much greater strength is required for the patient to be able to return to his vocational or avocational activities.
Studies of the hand have shown that a finger is fully flexed by the flexor digitorum profundus and the extensor digitorum communis. Additionally, when resistance is added, the flexor digitorum superficialis, the interossei and the intrinsics of the thumb are also activated. Therefore, by using a resistive exercising device, many muscles are forced to function. It has also been shown that the extensor digitorum communis, the flexor digitorum superficialis and the flexor digitorum profundus perform in direct proportion to the external load applied. Therefore, any hand exerciser employed should provide for increasing resistance.
Many hand exercising devices are known. Exemplary are the devices shown and described in U.S. Pat. Nos. 689,652; 756,480; 3,216,259; 3,357,702; 4,226,412; and Re. 28,845. Unfortunately, each of the devices suffers from one or more of the following disadvantages. First, the contact area between the palm of the hand and the grip of the device should be maximized in order to decrease the pressure in the thumb web space. This generally requires a contoured grip which fits along the curve of the oppositional crease, and one which is slightly convex so as to rest in the concavity of the palm formed by the transverse metacarpal arch. Many of the known devices do not include such a grip.
Second, the transverse portion of the exerciser which is actually engaged by the fingers and compressed toward the grip should be angled so as to conform to the hand. The transverse palmar axis passes along a line from the second to the fifth metacarpal heads. This forms an angle of approximately 75 degrees with the axis of the third ray. Furthermore, by angling the transverse mechanism, the fourth and fifth digits assist in initiating flexion. This is significant since the fourth and fifth digits are primarily responsible for power gripping in normal hands. Most of the known devices do not include such an angled transverse mechanism.
Third, the prior art devices do not include means for conveniently altering the stroke distance of the device so as to accommodate hands of different sizes nor do they provide a transverse mechanism which is not only angled but also rotatably mounted. The rolling feature created along with the ability to change the stroke distance of the transverse mechanism provides for complete flexion of the digits, thus permitting complete joint range of motion and full tendon excursion. These two factors are necessary for normal hand functioning.
Fourth, the prior art devices do not include means associated with the transverse portion of the exerciser that compensate for the different lengths of the fingers that grip the transverse portion. The middle and last two fingers have different lengths, therefore, it is necessary to provide a transverse portion of the exerciser that will accomodate and compensate for the differing lengths of these three fingers.
Finally, it is very important that the amount of resistance presented by the device be capable of being varied. It is especially important that this be easily accomplished with one hand during the early stages of hand rehabilatation. Such adjustments are difficult in the prior art devices.